The invention concerns an automobile ride leveler system.
A ride leveler system of this type is known by way of example from German Patent DE 196 40 149 A1. This known ride leveler system has wheel suspension devices in the form of pneumatic spring devices. The height sensors measure actual distances between the vehicle axles and the automobile body at the same time as the actual height differences between an automobile wheel and the automobile body. If a preset deviation between target and actual height is present, in this known ride leveler system the switch-off time of the adjustment of a wheel suspension device is set depending on the trailing behavior of the vehicle body. This is intended to prevent overshoot behavior. This system does not account for the danger of premature switch-off of the adjustment.
In other ride leveler systems, which are active even while the vehicle is in operation, when a deviation between target and actual level occurs, ride leveling is executed until the level sensor first senses the value of the target height or target level. In order for attainment of the target level with ride level regulation by means of height sensors to be recognized as delay-free as possible, a relatively fast filtration of the sensor signals is necessary. As a result, however, the sensing of road stimulations is essentially unfiltered. Ride level regulation can, as a result, be recognized as terminated before the actual attainment of the target level if the target level is detected by the height sensor for a brief period as a result of spring deflection and rebound.
The object of the invention is to improve a ride leveler system of the type mentioned above in order to prevent the danger of premature switch-off of level regulation.
The ride leveler system in vehicles according to the invention has an adjustable wheel suspension device between a vehicle wheel and the vehicle body, a height sensor for determining the actual height between a vehicle wheel and the vehicle body, and an electronic control device. A wheel suspension device and a height sensor may, for example, be provided for each vehicle wheel or only for the vehicle wheels of one axle. The control device specifies a target height and causes the adjustment of the wheel suspension device until the attainment of the target height, as long as there is a deviation between target and actual height. Fundamentally there should be no deviation between target and actual height, although ordinarily there will be a tolerance range in order to avoid too frequently occurring regulation. When there is a deviation between target and actual height, which preferably is greater than the specified allowable deviation, the electronic control device accordingly begins to adjust the wheel suspension device for a specified minimum control period depending on the path of the actual height. After expiration of the minimum control time, the control device does not switch the adjustment off until the measured actual height first attains the target height or has already exceeded it.
Preferably the minimum control period is specified through empirically determined experimental values, stored in the control device, of the adjustment speed for the particular wheel suspension device and control device used depending on the deviation to be compensated.
During the minimum control period, level control can thus not be recognized as terminated on the basis of a signal from the height sensors. Only after the expiration of this specified minimum control period are the preferably quickly filtered height sensor signals used for recognition of attained target level. Thus, a spring deflection and/or rebound, during which the target level is briefly attained, does not result in a premature termination of level regulation during the minimum control period. As a result of the minimum control period, there is a guaranteed minimum adjustment travel which contributes to an enhancement of the quality of regulation, in particular, in the case of strong road stimulation, as for example, in the case of a bad stretch of road or wavy road surface. As a result, there is a reduction of the frequency of regulation. Furthermore, in the case of a lowering or raising of the vehicle level for safety reasons, no condition is signaled to the driver which has not yet been attained.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.